Muffle kiln



L. W. MANION Nov. 8, 1932.

MUFFLE KILN Filed Oct. 7, 1931 4 Sheets-Sh'eet 2 L. W. MANION Nov. 8, 1932.

MUFFLE KI LN Filed. Oci. 7.

1931 el Sheets-Sheet INVENTOR By bea %ZA/union %ga/M: ATTORNEYJ Patented Nov. 8, 1932 UNITED STATES' mam i LEO W. MANION, OF CANTON,

MUFFLE KILN Application filed October 7, l3lif's erial No, 5673105.

'My invention relates to kilns adapted for burning clay, shale, and other ceramic products, including brick, tile, and the like,' by the use of indrect heat, and particularly 5 adapted for burning glazed ceramic products by the use of indirect heat.

In the usual kiln used for burning brick, tile and the like,`the distribution of the heat throughout the burning chamber is notuni- 10 form, and the products being burned are subject to the direct action of the burning vor heating medium, resulting in the case of glazed products, in a burned producthaving non-uniform surfaces.

Moreover, in the usual kiln the total quantity of heat available in the burning or heat-- ing medium is utilized to a' relatively limited degree.

The objects of the present improvements include the provision of a kiln adapted for burning ceramic products, in which the products being burned are not subject to the direct action of the burning or heating medium, in which the total mass of products being burned is subject to a substantially uniformly distributed heat, in which a greater quanti'ty o' the total heat content of the heating me-` dium is utilized than in ordinary kilns, in owhich the heating medium may be 'controlled 'and in which the interor is easily accessible for charging the green products and emptying the burned products.

The foregoing and other objects are attained by the kiln structure, parte, improve- 9 mente, and combinations, which comprise the present invention, and which are particularly and distinctly pointed out and set forth in v the appended claims forming part hereof.

In general terms the improved mufile kiln:

40 hereof includes walls forming an outer chamber, and walls forming preferably two inner chambers each inner chamber being located within the outer chamber and being spaced th-erefrom and from the other inner chamber,

the outer chamber preferably includin a circular bottom wall, a cylindric side wall', and a' dome top wall, and each inner chamber including a segment-al bottom wall which may comprise a part of the bottom wall of the` outer chamber, side walls including a semi-' cylindric wall connecting at its ends with a straight vertical wall, 'and a preferably removable top wall, the semi-cyclindrc. wall of each `'inner chamber being spaced froni the inner surface of thepreferably cylindric side' u wall of the outer chamberg and the straight vertical walls of the pre'fe'rably' two inner chambers being spaced from'eaohothercen trally with respect to the outer chamber, walls forming preferably a plurality of combustion chambers for each' inner chamber "and walls forming communicating flues ex'tending from the combustion chambers ;beneath the bottom wall of 'each' inner cha'mber," thence between the central'spaced straight vertical side walls of the inner chambers and between the outer surface of each semi-cylindric'wallof each inner chamber and the oppos'ite'inner surface of the cylindric side wall ofthe outer chamber', thence across the top of each inner cha-mber', thence through a downtake fiue for each inner chamber, thence through a -preferably horizontal eXhaust flue below each inner chamber, and thence to an exhaust stack.

A preferred embodiment of the present i mprovements is illustrated in the accompanying drawings forming part hereoflin which i Figure 1 is avertical sectional View of the improved kiln, as on lines 1-1 Figs. 3 and 4;

Fig, 2, a similar sectional View thereoi', a s so" on lines 2 2, FigsB and 4; i

Fig. '3,' a horizontal sectional View thereof, as on lines 3 -3, Figs; 1 and 2; and' i Fig. 4, a horizontal sectional view thereof, as on lines H, Figs. '1 and2. Similar numerals refer to similar parte throughout the 'several views. v

The improved mufile kiln is indicated gen erallyby 10 and includes walls forming an outer chamber indicated generally by 11, and walls forming preferably twonner chambers indicated generally respectively by 12@ and 126.

The inner chamber walls are located within the outer ch'amber walls and are spaced therefrom and from each other in a novel manner as will here-matter be set forth in greater detail. i The wallsforming the outer chamber 11 pref-erably include a circular bottom wall 13 dric sidewall '14 extending upwardly 'and i downwardly from the bottom wall, and a i dome topwall provides aclosure for the way openingsa and 256 forned respec- 6 upper end of the cylindric side wall 14.

i The side'walllt has preferably formed therein diametricallyopposite doorway openi ings 16a and166 through which access may v be had to the inner chambers as will be herein after set forth in greater detail. As illustrated, closure walls way openings 16@ and 166 for the 'reason that the drawings illustrate the arrangement and 'relatonship of the variouskiln walls" and other parts when a change is being fired the charge beingillustrated only in' dot-dash i lines inboth ,of the inner muflled chambers 12d'0r126 inorder that the structure' and i -arrangementof- 'the improved kiln may ;be

more clearly shown.

The walls formng the inner chamber `12a include a segmental'bottom wall 18a which e as illustrated comprises apart of the' bottom wall 13 of the outer chamber-'lL Side walls eXtend-upwardlyfrom the outer peripheryof the bottom wall 18a and include i ;the bottom wall 13 of the outer chamber 11.

Side walls extend upwardly 'from the outer periphery of the bottom wal1'186, and include* a semi-cylindric wall 196 conneoting at its ends witha straightvertical wall 206. j V

i The -inner chamber126 ispreferably completed by a preferably removable top wall The semi-cylindric wall-19a of the inner chamber 12a isspaced from one substantially T semi-cylindric portion of the inner .surface.

4 of the cylindric wall 14 ofthe outer chamber 11; and similarly the semi-*cylindric wall 196 of the inner chamber 126 is spaced from* the othersubstantially semi-cylindric por- '50-tion of the inner surface of the cylindric i wall ltof the outer chamber 11. v u

The straight vertical walls 20@ and 206 are preferably parallel with each other and on opposteasdes of andparallel with a' vertical diametral plane Y -Y,of the outerchanber 11. I rr As best'illust''ated in Figs. 3 and 4' the central rectangular sections 2200 and 226. respectively of the walls 20a and 2067 are'greater in thickness than the other portions of the wall, for providing structural strength, and for forming a door frame with wallsc 22cand 22d extending vertically and transversely between the walls 22a and 226.

55 p As illustrated closure walls 23a and 236" 1760 and i have been builtnp respeotively in the door- A Y tively in the cylindrio walls l d and196and 1 withthe doorway openings 16a and 166 of the'outer chamber cylindric wall 14.

The doorway openings 2565 and 256 have closure walls 26& and 266 built up therein,

as 'illustrated Accordingly when the several closure walls 'are removed from the severalalinedg against the inner surface of the eylindric wall 14, and the columns 27c-and 27 d extend between the walls 2006 and" 206 whose'outer ends terminate in the columns 27 c and 27(Z,

andthe outer ends of the semi-cylindric walls i 19aand 196 likewise terminate in the columns 27'@ and 27 d., v

Ajcentral vertical flue forming' wall 280 extends between'the column27 and the all 7220, and the wall 280 is parallel with and i spaced from the opposite portions 'of the walls 20@ and 206. 4 i Similarly, a central Vertical fine forming 2703 are I preferably loi 'doorways, access maybe had with either of the inner c hambers'12a or 126 through either of the doorwayopenings 1605 or166 for the wall 2861 extends between the wall 220? and;

the column-2766,` and the wall 28(Z is para llel t with and spaced from the opposite pcrtions of the walls20a and 206. y

An arch wall section 286 conneets the upper inner ends ofithe walls 280 and 28d between and above the walls 220 and 226%. i A plurality of circumferentially spaced partition posts 29a 'are interposed between the semi-cylindric wall 1901 and the cylindrie 1 'wall ly forminga plurality of arcuate up- Wardly extendingfiues 30a, one wall of each of which is formed by the semi-cylindric wall l9a. i e

For similar purposes, aplurality of spaced partition posts 31a are interposed between the wall 280 and the' opposite portions of' the wall 20a, and betweenrthe wall 2866 and the opposite portions of the wall 200?, form ing a plurality of upwardly extending` fiues' 3260, one wall of each of which is formed'by 1 the wall 2005. I

Similarly, a plurality of'circumferentially p spaced partiti'on posts 296 are interposed be tween the senicylindric wall 196 and the cylindric wall 14, forming a plurality of.

arcuate upwardly extending fiuesS06 one r Wall of each of which is formed by the semir.

cylindric wall 196. i

For similar purposes a plurality of spaced partition'posts 316 are interposed between the wall 280 and the oppositepo-rtions of the wall 5 206, 'a'nd between the wall 2866 and the PPO:

site portions of the wall 206, forming a plurality of upwardly extending fiues 326, one wall of each of which is formed by the wall 206. y

As illustrated, the doorway opening is formed in a frame interposed in the wall 19@ and, including side posts 33@-1 and 33@-2, and the side posts 33@ 1 and 33@-2 eXtend between the wall 19& and the wall 14 and form therewth as illustrated, uptake flues 3060-1 and a-2 at each side of the doorway opening 25@ e v Opposite faces 34a-l and 34a-2 of the side posts 33@-1 and 33a-2 rcspectively are parallel with each other and alined respectively with the parallel side faces 3506-1 and 35@ 2 of the doorway opening 16@, and these alin'ed opposite side faces form with the opposite parallel faces of the closure walls 17@ I horizontally and 26a, the inner faces of a Vertically extending; downtake fiue 36a.

Similarly the doorway opening 256 is formed in a frame interposed in the wall 196 and including side posts 336-1 and 336-2, and the side posts 336- 1 and 336-2 extend between the wall 196 and the wall 14 and form therewith as illustrated, uptake flues 306-1 and 306-2 at each side of the' doorway opening 256.

Opposite faces 346- -1 and 346-2 of the side posts 336-1 and 336-2 respectively are parallel with each other and alined respectively with the parallel side faces 356-1 and 356-2 of the doorway opening 166, and these alined opposite side faces form with the opposite parallel faces of the clo-sure walls 176 and 256, the inner faces of a Vertically eX- tending downtake fine 366.

A fiue 37a-1 is formed at one side of the doorway 246: by the wall 220, portions of the wall 20c, one of the partit-lon posts 31@, and portions of the wall 280; anda fine 37@-2 is formed at the other side of the -doorway 24@ by the wall 2266, portions of the wall 20@, one of the partition posts 31a, and portions of the wall 2806.

Similarly, a flue 376-1 is fo-rmed at one Side of the doorway 246 bythe wall 2206,

portions of the wall 206, one of the partition posts 316, and portions of the wall 280; and a fine 376-2 is formed at the other side of the doorway 246 by the wall 2261, portions of the wall 206, one of the partition posts 316, and portions of the wall 2862. e

A central heating chamber 38 is formed by the central portion 40 of the bottom wall 13 closing the lower ends of the opposite parallel wall sections 22@ and 226 and the opposite parallel Walls 220 and 22d which eXtend between the wall Sections 22@ and 226.

The wall 220 has formed therein horizontally extendng apertures 39a -1 communicating between the fiue 3704-1 and the chamber 38; and the wall 22@ has formed therein extending apertures 39a-2 communicating between the flue `37@-2 and the chamber 38. V

An upper circulating chamber 41@ is formed between the upper wall 21@ forc the inner chamber 12@, the opposite portions of the dome wall 15 and one side of the upper ends of the walls 280, 2865, and 280; and an upper circulating chamber 436 is formed between the upper (wall 216 for the inner chamber 126, opposite portions of the dome wall 15, and .the other side of the 'upper ends of the walls 280, 280Z, and 286' The tops of the walls 280, 28d, and 286 terminate in a common upper face 42 located below the'under face 43 of the dome or crown Wall 15, thereby forming an opening 44 communicating between the circulating chambers 41@ and 416.

I The upper ends of the several fiues 300 30@-1, 3004-2, 32@, and one side of the 'upper end of the central heating chamber 38 communicate with the upper circulating chamber 41@ r i Similarly, the upper ends of the several fiues 306,' 306-1, 306-2, 326, and the other side of the upper end of the central heating chamber. 38 communicate with the upper cira culating chamber416.

Likewise, the upper end of the downtake flue 36@ communicates with the upper circulating chamber 4161,' and as illustrated the downtake flue 36@ is preferably located on the outside of the sem-cylindric wall 19a and midway wall 2005.

I Similarly, the upper end of the downtake flue 366 communicates with the uppercirculating' chamber 416, and as illustrated the downtake flue 366 is preferably located on the outside of the semi-cylindric wall 196 and nizlway between the ends of the Vertical wall VValls indicated generally by 45@ form a preferably horizontal exhaust and heater fiue. 46@ beneath the inner chamber 12@, and the y walls 45@ forming the fiue 46@ preferably include portions of the se mental bottom wall 18@ of the inner chamber 12@, which as aforesaid comprises a part of the bottom wall 13 of the outer chamber 11. i

The outer end of the flue 46@ communicates with the lower end of the downtake fine 36@ VValls indicated generally by 47@ form a central Vertically extending intermediate eX- haust flue 48@ which communicates at its upper end with the inner end of the fiue 46@; and walls indicated generally by 49@ form a diagonally extending preferably horizontal exhaust flue 50@ which communicates at its inner end with the lower end of the intermediate flue 48@, andwhich extends beyond the kiln to an exhaust stack, not shown.

Similarly, walls indicated generally by 456 form a preferably horizontal exhaust and heater flue 466 beneath the inner chambetween the ends' of the vertical' ber 123), and the walls 45?) formingthe flue 46?) preferably include portions of thegsegmental bottom wall 186 `ofthe inner chamber 12b,`Whieh as aforesaid comprisesca part of the bottom wall 13 of the outer chamber The outer end of the flue 46?) communicates I with thelower end of the downtake flue 86b.

`Walls indicated generally by 4:7?) form a central Vertically extending intermediate-exhaust fiue &825 which communicates at its upper endwith the inner end of the flue ib and walls indicated'generally by 495 forma diagonally eXtending preferably horizontal exhaust fiue 506 which communicates at its i inner end with the'lower end of the intermediate fiue 503), and which extends beyond the kiln to an exhaust stack, not shown.

As illustrated, the walls 47& and 47 5 forming the intermediate exhaust fiues 48@ and &Sbiilude :t common partition wall 51, and the partition ,wall 51 extends and forms a common end closure'for the exhaust and i'espectively.

introduced into the lower ends of the several' i i fiues 30@ &Qaa-1,' %ae-2, 3200, 37a-1, and 3764--2 flows upwardly about the walls 19a heater fiues 46@ and 466, and thecommcn partition walll furthermore extends and forms a common, partitionwail of the walls 4:9a and 49?) forming the fiues 500; and 501),

By the foregoing Construction and arrangement of the kiln 10, heating medium and 200, transferring heat to these walls and thence to the charge within the chamber l2a, and theheating medium furthermore fiows from the flues 37a-1 and the fiues 37a-2 respectively through the horizontal apertures SQa-l and 39a-2into the central heating chamber. 38, `and the heating medium then fiows out of the upper ends of all of the afore said tlues 30a, 30a-1, 30a-2, 32c, 37w-l and and Efica-2, and out of the upper end of the 'central heating chamber 38into the' upper circulating chamber la, and flo ws therein over the top Wall Qla into the upper end of the v downtake fiue 36a, the curvature of the inner surface of the Wall 14 and the curvature of the under face 43 of the deme or erown wall 15 eerving to deflect the heating medium towards the centrally located upper end of the. 'downtake flue 36a and the heating medium fiows downwardly through the fine 36a into the horizontal eXhaust and heating flue 46@ and thencethrough the intermediate exhaust fiue 48@ into the exhaust flue 50@ which delivers the heating medium to an exhaust sta'ck not shown.

This flow oI". heating medium about the side Welle and over the top wall of the inner chember 12& is illustrated in thedrawings by the errows end a similar flow of heating medium takesplace aboutthe side and top walls of the chamber 126. y V i The i present invention furthermore includes means for simultaneously heating the bottom wall 'and supplying a yariable quantty'of heating' medium-to the aforesaid flues and circulating chambers about the sides and top wall of each inner chamber.

v The combined bottom wall heat supply means for thesides and top walls of each inner chamber, include for the inner' chamber 12a, walls' forming a plurality of combustion chambers 52a-1, 52'a l, 52"a-1, 52"a-2, 52'a-2, and 520-2.

The source of heat 'for each combustion chamber as illustrated is an oil burner 53.

Walls including portions of the bottom wall 18a form a labyrinthian flue indicated generally by Mac-l below the bottom wall 1806, and the combustion chamber (Baa-l communieates with the outer end of the labyrinthian fi ue '54a-1, and the labyrinthian flue 54L-1 communicates with the lower end of one of the flues 30a and' with the lower ends of a plurality of' the' flues 32c. i

VValls including portions of the bottom* wall 18@ form a labyrinthian fiue indicated generally by Mat-2 below the bottom wall l8a, and the combustionchamber 52a-2 communicates withthe outer'end of the laby- `rinthian fiue Sea- 2 and the labyrin'thian fiue 54`a-2 communicates with the lower endet one of the flues .3005 and with the lower ends of a plurality of the flues 3209.

As best illustrated 'in Fig. 4:, the combust1on chamber 52w-1 and its labyrinthian fiue 54w-1 are symnetrieal about the aXis X-X.

with the combustion chamber 52a -2 and its labyrinthian fiue 54a-'-2. t

Walls including portions of the bottom Wall 18a 'form a labyrinthian flue indicated generally by 54'c-.1 below the bottom wall 1866, and the combustion chamber 'c-l communicat-es with the outer end of the heating and labyrinthian fiu-e ,54'0 -'-1, and the labyrin i thian flue 54'a-1 communieates with the lower end of one of the fiues 30@ and With the lower end of one of the flues 32&

VValls including portions of the bottom' fiue A'e-1 are symmetrical about the axis' X-X with the combustion chamber, 52'64-2 with its labyrinthian fiue 'cw-Q.

VValls including portions OI" the bottom wall lSa'form a lubyrinthian fiue indicated generally by 54%& 18& and the combustion chamber 52% 2-1 communicates with the outer end of the labyrinthian flue 54:"c-1, and the labyrinth l below the bottom wall v ian flue 54:"41-1 communicates with the lower end of the fiue 30a-1 and with the lower end of the fiue 37a-1. i V

'Walls including portions of the bottom wall 18@ form a labyrnthian flue ndicated generally by 5L"a-2 below the bottom wall 186; and the combustion chamber 52"co-2 communicates with the outer end of the labyrinthian fiue 54"a-2, and the'labyrinthian flue "a-2 communicates with the lower end of the fine 3060-2' and with the lower end of the fiue ?fle-;2.

Asbest illustrateol in Fig. 4: the combustion chamber 52"c-1 and its labyrinthian flue 54"w-1 are symmetrical about the axis X-X with the combustion'chamber 52"c `-2 and its labyrinthian flue 54:"a-2;

I Walls including portions of the bottom wall 18?) form a labyrinthianflue indicated generally by 546-1 below the .bottom wall 186, and the combustion chamber 526-1 communicates with the outer end of the labyrinthian fiue Ab- 1, and the labyrinthian fine' 546-1 communicates with the lower end of one of the ues 30?) and with the lower ends of a plurality of the flues 327).

`Walls including portions of the bottom Wall 18?) form a labyrinthian fiue indicated generally by b below the bottom wall 186, and the combustion chamber 526-2 communicates With the outer end of the labyrinthian fiue 546-2, and the labyrinthian fiue 545-2 communicates with the lower end of one of the flues 30?) and with theloWer ends of a plurality of the fiues 327). i

i As best illustrated in Fig. 45, the combustion chamber 5212-& and its labyrinthian flue tb-l are symmetrical about the aXis X-X with the combustion chamber 525-2 and its VValls including portions of the bottom wall 187) form a labyrinthian flue indicated generally by 54'b-1 below the bottom wall 18b, and the combustion chamber 52'6-1 communicates with the outer end of the labyrinthian fine 54'6-1, and the labyrinthian flue 54'6-1 communicates with the lower end of one of the fiues 30band with the lower end ot one of the flues 327). g

Walls including portions of the bottom wall 18?) form a labyrinthian flue indicated generally by 54'b-2 below the bottom wall 181), and the combustion chamber 52'6-2 communicates with the outer 'endi of the labyrinthian fine t'b-, and the labyrinthian flue 54'19-2 communicates with the lower end of one of the fiues 306 and with one of the flues 321).

As best illustrated in Fig. 4, the combustion chaniber 52'5-1 and its labyrinthian fiue i'b-l are symmetrical about the aXs X-X with the combuston chamber52'b-2 with its labyrinthian flue 54'6-2.

WValls including portionsof the bottom wall 18?) form a labyrinthian fiue indicated rinthian'fiue 5%"6-2, and the labyrinthian V flue 5%"6- 2 communicates with the lower end of the fiue 306--2` and with the' lower' end of the flue ?Kb-.2. I i i As best illustrated in F ig. i the combustion chamber 52"b-1 and its labyrinthian fiue 5 1"b'-`-1 are symmetrical about the aXis X-X with the combustion chamber 52"b`-2 and its labyrinthian flue 54"b-2.

One'or more doorway frames 55a, each fitted with a door 56a, are provided' in the walls 14: and 19a;and similarly one or more doorway frames 556, each fitted with a door 5604,

are provided in the walls 14 and 197), for i permtting Water smoking of the ch'ambers 120; and 126. r i i Accordingly, by the foregong arrangement of the coinbustion chambers and flues, each combustion chamber provides heat for a sectoral Zone of the inner chamber heated thereby, and the heat supply for each com bustion chamber may be varied so as to regulate the heat in the several Sectoral zones of eachiinner chamber, whereby a uniform distribution of heat may be attained' in each inner chamber. i 7 i I claim: i i

1. A kiln including walls forming an outer chamber, walls forming two inner chami bers, each inner chamber being located within the outer chamber and being spaced there-v from and from the other inner' chamber, the walls forming the outer chamber including, a bottom wall, curved 'side walls, and a top wall, andthe walls forming each inner chamber including a segmental bottom wall, side walls including a curved walland a sub-, stantially straight wall' connectedat their ends with each' other, the'curved wall of each inner chamber being spaced from. op posite portions of ,the inner surface ofthe curved side walls of the outer chainber, and the substantially straight walls ofthertwo inner chambers being spaced 'from 'each other and being located centr'ally With respect to the outer chamber, the top ofeach inner chamber being spaced belowthe top wall of the outer cham'ber and there being formed a circulating chamber therebetween, walls forming a, 'downtake flue for each inner' i chamber, the upper end of each downtake" 7 :chambers at the lower ends thereof a suppl'y of heating' medium' between 'the spaced walls forming the enter' and inner 2. 'A'fkiln including walls forming an outer chamber, walls forming two'inner chambers'each inner chamber beinglocated withinthe outer chamber andbeing spaced there-j from and from the other inner chamber, the

` walls forming .the outerzchamber including 6 a'bottom 'wall, curved side walls,and a top ber includinga segmental bottom wall, side' wall, 'and the walls forming each innerchami walls including a curved wall and a wall connecting the ends of the curved wall, the curved wall off each inner. chamber :being spaced from opposite portions 'of the inner surface of the curVed side walls of the outer chamber, and the connectingwalls of the two inner chambers being spaced from each other and being located centrally 'with re-' e spect to the 'outer' chamber, the top of each inner" chamber being spaced below the 'top wallof the outer chamber andthere being' fformed a circulating therebetween, walls forming. a downtake flue for each inner chamber, the upper end of each downtake fiue communicating with the adjacent circulating chamber, and means for introducing i a supply of heating medium between the spaced walls forming thejouter and inner chambers at the lower ends thereof.

3. A kiln including walls forming an outer chamber, walls forming' two inner 'chambers each inner chamber being located within the oute r chamjberf andbeing spaced therefrom i and from the other inner chamber and walls forming the outer chamber including a bottom wall, side walls, and a top wall, and the walls forming each inner chamber including a bottom wall and side walls; portions of the sidewalls of each inner chamber being spaced from opposite portions of the inner surface ?of theside walls of the outer chamberyand i portionsof the'side walls of each inner chamber being centrallyi located and spaced from the centrally located' portions of the side walls of the other inner chamber, the top of each inner chamberbeing spaced below the top !wall of the oufer chamber' 'and there being formed a circulating chamber therebetw'een, walls forming an eXhaust flue for each circu lating chamber, each exhaust fiue communicating 'with its circulating chamber, and l means for' introducing a supply of heatng mediumbetween 'the spaced side wallsof the chambers at 'the lower ends thereof.

- 4. %A kiln including walls forming an outer' chamber, wallsforming two inner chambers,

walls forming each inner chamber including "a 'bottomwalland side walls,` portions of the emi side wallsrofeach inner .chamber "spaced from 'opposite portions 'ofethe inner surface of the side walls of the outer chamber, and

portions of 'the side walls of each inner chamber being centrally located and spaced from the centrally located portions'of the side 'walls of the other inner chamber, the top 'of each inner chamber being spaced below the top wall of the outer chamber and there being i formed a circulating chamber therebetween,

walls' forming anexhaust flue for eachcirculatng c hamber, each eXhaust flue communicating with its circulating chamber; walls forming a heater fiue beneaththe bottom wall of eachinnerchamber, there being formed an exhaust opening for each heater fiuebe-` tween opposite spaced side walls of the cham-` a bers at the lower' ends thereofgand means for introducing a supply of heating medium into each heaterfiue. e v 5." A kiln including walls forming an outer. chamber, walls forming two inner chambers,

each inner chamber being located within the outer chamber and being spaced. thereffom and from the other inner chamber, the walls' forming the outer chamber including a'bottom wall, side walls, and a topwall, and the i i walls forming each inner chamber including a' bottom wall and 'side walls, portions of the side walls of each inner chamber being spaced from opposte portions of the inner surface of the side walls of the 'outer chanber, and' portions of the side walls of each inner chamber being cent'rallylocated and spaced, from the centraily located portions of the side walls of the other inner chamber, the 'top of' each,

inner chamber being spaced below the top wall of the outer chamber and there being form'ed a circulating chamber therebetween,'

walls forming an exhaust flue for each circu: lat ng chamber, each exhaust flue communicating with its circulatingchamber; walls" forming a heater flue beneath the bottom ,wall ofeach inner chamber, there being formed an exhaust opening for each heatr fiue *between the spaced sidewalls of the inner and outer chambers at' the lower ends thereof, and

' there beingformedanother exhaust opening for each heater' flue between the. spacedside walls of theinner chambers at the lower end s thereof; and means for introducing a supp'y of heating medium into each heater flue.

6. 'A kiln including walls forming an outerchamber, wallsforming two inner chambers,

each inner chamber being located within the outer chamber and being spaced therefrom and from the other in'nerchamber, the walls forming the iouter chamber including a bottom wall, side walls and a top wall; and the walls forming each innerchamber including a bottomwall and side walls, portions of the sidewalls of eachinner chamber being spaced from opposite portions of the inner surface i' of the side wallsof the ;outer chanber, and, portions'of the side walls' of each inner Cham iz'o ber being centrally located and spaced from the centrally located portions of the sidewalls of the other inner chamber, the'top of each inner chamber being spaced below the top wall of the outer chamber and there being formed a circulating chamber therebetween, walls forming an exhaust fiue for each circulating chamber, each eXhaust fiue communicating with its circulating chamber, walls formin g a heater fiue beneath the bottom wall of each inner chamber, there being formed an exhaust opening for each heater fiue betwecn the opposite spaced side walls of the i nner chambers at the lower ends thereot, and means 'for introducing a supply of heating medium into each heater fiue.

7. A kiln including walls* forming an outer chamber, walls forming two inner chambers,

each inner chamber being located within the outer chamber and being spaced therefrom and froni the other inner chamber, the walls fcrming the outer chamber including a bottom wall, side walls, and a top wall, and the walls forming each inner chamber including a bottom wall and side walls, portions of the side walls of each inner chamber being spaced from opposite portions of the inner surface of the side walls ot' the outer chamber, and portions of the side walls of each inner chamber being centrally located and spaced from the centrally located portions of the side walls of the other inner chamber, the top of each inner chamber being spaced 'below the top wall ot the outer chamber and there being formed a circulating chamber therebetween, walls forming an exhaust fiue f'or each circulating chamber, each eXhaust fiue communicating with its circulating chanber, p walls 'forming a plurality of heater fiues beneath the bottom wall oi' each inner chamber, there being fai-med an exhaust opening for each heater fiue between opposite spaced side walls of the chambei's at the lower ends thereof, and means tor introducing a supply of heating medium into each heater fiue.

8. A kiln including walls forming an outer chamber, walls forming two inner chambers,

each inner chamber being located within the outer chamber and being spaeed therefrom and from the other inner chamber, the walls torming the outer chamber including a bottom wall, side walls, and a top wall, and the walls forming each inner chamber including a bottom wall and side walls, porti ons of the side walls of each inner chamber being spaced treni opposite portions of the inner surface of the side walls of the outer chamber, and

portions of the side walls ot each inner chamber being centrally located and spaced from the centrally located portions of the side walls of the other inner chamber, the top of eachinner chamber being spaced below the top wall of the outer chamber and there being formed a circulating chamber therebetween, walls forming an exhaust fiue for each circulating chamber, each eXhaust fiue co'nmunicating with its circulating chamber, walls forning a plurality of heater flues beneath the bottom wall of each inner chamber, there being formed an exhaust opening for each heater fiue between the spaced'side walls of the inner and outer chanbers at the lower ends therof, and there being, formed another exhaust opening for each heater 'fiue between the spaced side walls of the inner chanbers at the lower ends thereof, and means for introducing a supply of heating medium into' each heater fiue.

9. A kiln including walls torming an outer chamber, walls formingtwo inner chambers, each inner chamber being located within the outer chamber and being spaced therefrom and from the other inner' chamber, the walls forming the outer chamber including a bottom wall, side walls,- and a top wall, and the walls forming each inner chamber including a bottom wall and side walls, portions of the side walls of each inner chamber being spaced from opposite portions of the inner surface of the side walls of the outer chamber, and portions of the side walls of each inner chamber being centrally located and spaced from the centrally located portions of the side walls of the other inner chamber, the top of each inner chamber being spaced below the top wall of the outer chamber and there bein formed a circulating chamber therebetween, walls forming an exhaust fiue for each circulating chamber, each eXhaust fiue conmunicating 

